‘This 14-mile motorway will carve through the Gwent Levels, dividing and destroying an ancient wetland that is one of the last strongholds for the shrill carder bee.’
Photograph: RSPB/PA

A five-month public inquiry begins tomorrow into the most destructive new road in a generation. The six-lane M4 through Newport is a little twisty and vulnerable to traffic jams, so the Welsh government wants to flex new borrowing powers to fund a £1bn-plus “relief” road.

This 14-mile motorway will carve through the Gwent Levels, dividing and destroying an ancient wetland that is one of the last strongholds for the shrill carder bee and the new home, as of last summer, to Wales’s first breeding cranes for 400 years. The road will wreck four sites of special scientific interest, supposedly protected for nature, and create a “Berlin wall for wildlife” across the marshes for otters, water voles and rare dragonflies.

I had assumed the bad old days of ripping up nature reserves for motorways were long gone, but the scale of wildlife destruction on the Gwent Levels is bigger than both the Newbury bypass and Twyford Down, which triggered mass protests in the 1990s.

The justification is “resilience”. The south Wales economy supposedly grinds to a halt when the M4 at Newport is jammed. Are we so rich (in borrowed money) that we can duplicate motorways?

Credit to the Welsh government for one positive piece of policymaking. Two years ago it appointed a commissioner, Sophie Howe, with a legal duty to advise ministers on whether projects offer a good deal for future generations. Last week Howe concluded the road was not a good deal. “Building roads is what we have been doing for the last 50 years and is not the solution we should be seeking in 2017 and beyond,” she said.

Will the Welsh government listen to its own commissioner? Cynics fear the public inquiry is a foregone conclusion. It isn’t – if enough local people join Howe and other campaigners in telling politicians they don’t want this divisive road.

California’s poster-cat

P22. Photograph: Associated Press

A new book and film are raising awareness of the lines we draw across landscape. Linescapes by the ecologist Hugh Warwick examines the impact of roads, railways and hedges on British wildlife. Meanwhile, a new documentary, The Cat That Changed America, examines Los Angelenos’ attempts to repair their divided habitat.

The film’s star is “P22”, a wild mountain lion first caught on camera in 2012, beneath the Hollywood sign. Somehow, when he was young, P22 crossed two of America’s busiest freeways to make his home in Griffith Park – eight square miles against the preferred big cat territory of 200 sq miles.

P22 has become a celebrity, a poster-cat for urban survival in fragmented habitats. His fans are now campaigning to raise $50m to build a wildlife bridge over the 101 freeway to link the Santa Monica mountains with surrounding hills. This won’t help P22 find a mate but it will assist other big cats and wildlife in urban California.

Green bridges are no panacea but they show a commitment to living better with other species. And there are no proposals for such crossings on the M4 relief road.

Wetlands reconnected

Wetlands are being painstakingly reconnected in Cambridgeshire’s Great Fen project, creating a nature reserve big enough to support rare species such as the swallowtail butterfly which disappeared long ago when these marshes were drained for agriculture.

A recent fundraiser saw families – equally painstakingly – build a giant Lego model of the Great Fen, complete with dragonflies, birds, beetles and one non-native species – a Star Wars X-wing. Reconnecting fragmented landscapes does not belong in a galaxy far, far away.